Antisense oligonucleotides (AONs) are complementary to a region of a target gene and are capable of hybridizing to the target gene sequence and inhibiting gene expression. Gene expression is inhibited through hybridization of an AON to a specific messenger RNA (mRNA) sense target according to the Watson-Crick base pairing in which adenosine and thymidine (uracil in mRNA) or guanosine and cytidine interact through hydrogen bonding. Two mechanisms are generally thought to account for these effects, the first being hybridization with impaired translation of targeted mRNA, the second being the induction of RNase H or similar enzymes with associated degradation of target mRNA. A major advantage of this strategy is the specificity of action with the potential for reduced side effects and lower toxicity, especially when applied directly to the site of action (topical treatment). This therapeutic strategy could potentially be applied to any disease in which overexpression of one or several genes is believed to be responsible for the presence or persistence of the disease. As a result, there have been numerous studies investigating the use of AONs as therapeutic agents for cancer and viral diseases.
The alveolar and airway epithelium is recognized as a dynamic barrier that plays an important role in regulating inflammatory and metabolic responses to oxidative stress, sepsis, endotoxemia, and other critical illnesses in the lung. The respiratory epithelium, in particular, is a primary target of inflammatory conditions/infections at the epithelial-blood interface, and is itself capable of amplifying an inflammatory signal by recruiting inflammatory cells and producing inflammatory mediators.
Asthma is a disease that affects 5 to 10% of the population that has doubled in prevalence in the last 25 years. This increase has been noted especially in infants after a viral infection of the airways (bronchiolitis), in children and in occupation-induced asthma. The recurrent breathing problems associated with asthma are often triggered by allergens but the exact cause of asthma remains to be elucidated. However, it is believed that agents such as viruses are involved in the perpetuation of the abnormal inflammation that is found in the airways of patients with asthma and, thus, the persistence of the disease.
For this reason, the current recommendation for first line therapy of asthma is a potent anti-inflammatory medication such as those containing corticosteroids and anti-leukotrienes. Although this approach is effective in many patients, some patients are not controlled with current anti-inflammatory medications. Corticosteroids are also potent immunosuppressives with long term side effects and have not been shown to be effective in the prevention of allergy or asthma. Anti-leukotrienes have some effect in allergy and asthma but are not as effective as corticosteroids.
Several inflammatory mediators play a role in the appearance and perpetuation of inflammation in the airways of patients with asthma. Some mediators attract the inflammatory cells into the airways either through chemotaxis of eosinophils (the chemokines: RANTES, eotaxins 1, 2, 3, MCP-3, 4 that act mostly in asthmatic inflammation through a receptor called CCR3) or through endothelial cell activation (IL-4, -13). Other mediators cause the priming and increased survival of inflammatory cells in the airways (IL-3, -4, -5, GM-CSF). These mediators thus consist of either specific chemokines for eosinophils or cytokines of the T helper lymphocyte type 2 phenotype (Th2: IL-3, -4, -5, -6, -9, -10, -13 and GM-CSF), (John A E. and Lukacs N W., 2003 Sarcoidosis Vasc Diffuse Lung Dis., 20:180-189; Blease et al., 2003, Expert Opin Emerg Drugs. 8:71-81). An improvement in asthma and general respiratory inflammation has been demonstrated when there is a decrease in these inflammatory mediators in the airways.
Allergy is a hypersensitivity to an allergen causing an undesirable immune response. Allergy is a disease that is extremely prevalent, for example atopic rhinitis, eczema and allergic conjunctivitis affect around 30% of the population. Allergy is characterized by abnormal IgE production and inflammation to an allergen. In the presence of IgE and allergen, effector cells, such as the mast cells degranulate and release inflammatory mediators leading to the recruitment of the same inflammatory cells that are found in asthma. In allergic rhinitis (i.e. hayfever), allergic conjunctivitis, nasal polyposis, chronic sinusitis, eczema, and atopic dermatitis, one finds the same excess in inflammatory mediators as those present in asthma. IL-4 and IL-13 are necessary for the production of IgE and the induction of the cells with a Th2 phenotype (Barnes P J., 2003, Cytokine Growth Factor Rev. 14:511-522; Schuh et al., 2003, Cytokine Growth Factor Rev. 2003, 14:503-510). Atopic disease is a generic name for allergic diseases which are developed by exposure to allergens, especially in individuals with a genetic propensity for being easily sensitized to allergens. Individuals having these predisposing factors readily develop an abnormal immune response to alimentary antigens and inhalants. Some specific examples of allergic diseases are bronchial asthma, atopic dermatitis, urticaria, allergic rhinitis, allergic conjunctivitis and allergic enterogastritis.
Chronic Obstructive Pulmonary Disease (COPD) is another example of an inflammatory airway and alveolar disease where persistent upregulation of inflammation is thought to play a role. Inflammation in COPD is characterized by increased infiltration of neutrophils, CD8 positive lymphocytes, and macrophages into the airways. Neutrophils and macrophages play an important role in the pathogenesis of airway inflammation in COPD because of their ability to release a number of mediators including elastase, metalloproteases, and oxygen radicals that promote tissue inflammation and damage. It has been suggested that inflammatory cell accumulation in the airways of patients with COPD is driven by increased release of pro-inflammatory cytokines and of chemokines that attract the inflammatory cells into the airways, activate them and maintain their presence. The cells that are present also release enzymes (like metalloproteases) and oxygen radicals which have a negative effect on tissue and perpetuate the disease. A vast array of pro-inflammatory cytokines and chemokines has been shown to be increased within the lungs of patients with COPD. Among them, important roles are played by tumor necrosis factor alpha (TNF-alpha), granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin 8 (IL-8), levels of which are increased in the airways of patients with COPD.
Cystic fibrosis (CF) is yet another example of an airway inflammatory disease. Lack of CF transmembrane conductance regulator (CFTR) Cl− channel function leads to progressive pulmonary damage, and ultimately results in death. The loss of functional CFTR in airway epithelial cells promotes depletion and increased oxidation of the airway surface liquid. Activated neutrophils present in airways produce large amounts of proteases and reactive oxygen species (ROS). Together these changes are associated with reduced mucociliary clearance of bacteria, activation of epithelial cell signalling through multiple pathways, and subsequent hyperinflammatory responses in CF airways. Both the NF-kappaB pathway and Ca2+ mobilization in airway epithelial cells are believed to be factors in the control of lung inflammation via regulated production of mediators such as IL-8 that participate in recruitment and activation of neutrophils, modulation of apoptosis, and control of epithelial barrier integrity. Excessive and persistent inflammation sustained by bacterial infections and an ongoing accumulation of airway neutrophils is a key factor in lung destruction in CF patients, and has prompted investigation into anti-inflammatory therapies.
Other examples of respiratory diseases where inflammation seems to play a role include: eosinophilic cough, bronchitis, acute and chronic rejection of lung allograft, sarcoidosis, pulmonary fibrosis, rhinitis and sinusitis.
Eosinophilic cough is characterized by chronic cough and the presence of inflammatory cells, mostly eosinophils, within the airways of patients in the absence of airway obstruction or hyperresponsiveness. Several cytokines and chemokines are increased in this disease, although they are mostly eosinophil directed. Eosinophils are recruited and activated within the airways and potentially release enzymes and oxygen radicals that play a role in the perpetuation of inflammation and cough.
Acute bronchitis is an acute disease that occurs during an infection or irritating event for example by pollution, dust, gas or chemicals, of the lower airways. Chronic bronchitis is defined by the presence of cough and phlegm production on most days for at least 3 months of the year, for 2 years. One can also find inflammatory cells, mostly neutrophils, with a broad array of chemokines and cytokines, within the airways in cases of acute or chronic bronchitis. These mediators are thought to play a role in the inflammation, symptoms and mucus production that occur during these diseases.
Lung transplantation is performed in patients with end stage lung disease. Acute and more importantly chronic allograft rejection occur when the inflammatory cells of our body, lymphocytes, do not recognize the donor organ as “self”. Inflammatory cells are recruited by chemokines and cytokines and release a vast array of enzymes that lead to tissue destruction and in the case of chronic rejection a disease called bronchiolitis obliterans.
Sarcoidosis is a disease of unknown cause where chronic non-caseating granulomas occur within tissue. The lung is the organ most commonly affected. Lung bronchioalveolar lavage shows an increase in mostly lymphocytes, macrophages and sometimes neutrophils and eosinophils. These cells are also recruited and activated by cytokines and chemokines and are thought to be involved in the pathogenesis of the disease.
Pulmonary fibrosis is a disease of lung tissue characterized by progressive and chronic fibrosis (scarring) which lead to chronic respiratory insufficiency. Different types and causes of pulmonary fibrosis exist but all are characterized by inflammatory cell influx and persistence, activation and proliferation of fibroblasts with collagen deposition in lung tissue. These events seem related to the release of cytokines and chemokines within lung tissue.
Acute rhinitis is an acute disease that occurs during an infection or irritating event, for example, by pollution, dust, gas or chemicals, of the nose or upper airways. Chronic rhinitis is defined by the presence of a constant chronic runny nose, nasal congestion, sneezing and pruritus. One can also find within the upper airways during acute or chronic rhinitis inflammatory cells with a broad array of chemokines and cytokines. These mediators are thought to play a role in the inflammation, symptoms and mucus production that occur during these diseases.
Acute sinusitis is an acute, usually infectious disease of the sinuses characterized by nasal congestion, runny, purulent phlegm, headache or sinus pain, with or without fever. Chronic sinusitis is defined by the persistence for more than 6 months of the symptoms of acute sinusitis. One can also find during acute or chronic sinusitis within the upper airways and sinuses inflammatory cells with a broad array of chemokines and cytokines. These mediators are thought to play a role in the inflammation, symptoms and phlegm production that occur during these diseases.
A neoplasm is an abnormal tissue growth that is uncontrollable and progressive. A malignant neoplasm is often characterized as a cancer. Cancer is the second leading cause of death in humans and is a general term for more than 100 diseases characterized by abnormal proliferation of immortalized cells. One of the mechanisms involved in the persistence and increase in cellular proliferation is the release of growth factors that act through cognate receptors. Amongst these growth factors, GM-CSF has been shown to be an important growth factor for several tumour cells. The chemokine receptor CCR3 was recently characterized in malignant B lymphocytes recovered from patients with chronic lymphocytic leukemia (CLL) and with hairy cell leukemia (HCL), (Trentin et al., 2004, Blood, 104, 502-508). Indeed, the transactivation of Epidermal Growth Factor Receptor (EGFR) through CCR3 chemokine receptor was found to be a critical pathway that elicits MAP kinase activation and cytokine production in bronchial epithelial cells (Adachi et al., 2004, Biochem. Biophys. Res. Commun. 320, 292-396). Inhibition of cancer cell proliferation via blockage of receptors for growth factors and/or chemokines may be important in the therapy of certain cancers.
Eosinophils are a type of white blood cell. They are granular leukocytes with a nucleus that usually has two lobes connected by a slender thread of chromatin, and cytoplasm containing course, round granules that are uniform in size and stainable by eosin. Hypereosinophilia is characterized by an increased number of eosinophils, often associated with allergies, asthmas and infections.
Uses of oligonucleotides directed against specific nucleic acid sequences coding for receptors for inhibition of inflammatory reactions is known. Co-owned International Patent Application Publication Nos. WO 99/66037 and WO 06/045202 describe AONs used for treating and/or preventing asthma, allergy, hypereosinophilia, general inflammation and cancer.
For potential clinical uses, AONs should exhibit stability against degradation by serum and cellular nucleases, show low non-specific binding to serum and cell proteins, exhibit enhanced recognition of the target mRNA sequence, demonstrate cell-membrane permeability and elicited cellular nucleases when complexed with complementary mRNA. It is well documented that oligonucleotides containing natural sugars (D-ribose and D-2-deoxyribose) and phosphodiester (PO) linkages are rapidly degraded by serum and intracellular nucleases, which limit their utility as effective therapeutic agents. Chemical strategic modifications have been described for oligonucleotides in order to improve their stability and efficacy as therapeutic agents. The main chemical changes included, modification of the sugar moiety, the base moiety, and/or modification or replacement of the internucleotide phosphodiester linkage. To date the most widely studied analogues are the phosphorothioate (PS) oligodeoxynucleotides, in which one of the non-bridging oxygen atoms in the phosphodiester backbone is replaced with a sulfur (Eckstein F., 1985, Ann. Rev. Biochem., 54: 367-402). Several AON generations have been developed and used for in vitro and for in vivo studies (Goodchild J., 2004, Curr. Opin. Mol. Ther., 2004, 6:120-128; Urban E. and R. Noe C R., 2003, Farmaco. 58:243-258).
It would be desirable to have improved AONs directed against nucleic acid sequences coding for pro-inflammatory receptors for inhibiting these receptors. Such AONs would be useful in the therapy and/or prevention of asthma, allergy, hypereosinophilia, general inflammation and cancer.